AT&T 76450 - Manual (Page 5)

Common Systems Connection Standards AT&T Services, Inc
Date: June 2013
ATT-TP-76450, Issue 15
Copyright © 2013, AT&T . All Rights Reserved.
Page 5
2 DC / AC Power Interconnection Standards
2.1 GENERAL
2.1.1 Nominal -48v DC
Nominal –48V DC is the standard platform for power delivery to all network equipment. If
manufacturer’s network equipment uses other than -48V DC, it shall be provided with internal
inverters and converters to meet the intent of this requirement. The design criterion of the
nominal -48V DC power is based on a normal operating voltage between -50V to -56.7 V DC,
with nominal rating of -48v DC and low voltage of -40v DC measured at the input terminals of
the network equipment.
2.1.2 AC Powered Equipment
Equipment shall preferably be DC powered. Equipment that requires AC power shall be located
in a room with one hour fire walls separated from DC powered equipment and be powered by
an inverter on the -48V DC power system. If the AC powered equipment cannot be placed in a
one hour fire rated area, it will require NEBS Level 1 compliance. The proposed use of inverter
fed AC powered equipment shall be reviewed by GES Common Systems on a case-by-case
basis and will only be approved when a comparable DC version of the equipment is not made
by the manufacturer or is not otherwise available.
2.2 DC Power Cabling
2.2.1 Redundant Power Feeds
Redundant power feeders are required for all network equipment. Each element/shelf/circuit
pack, whichever is the smallest independent load device of the equipment, shall obtain power
from at least two power feeds.
2.2.2 Power Feeder Information
Redundant power feeder information must be provided in the supplier's response
documentation to be in compliance with this item. Power feeds (supply and return ) provided by
manufacturer’s shop wired configurations shall be paired and closely coupled.
2.2.3 Battery Return Conductor
Each power feeder shall have its own battery return conductor. This design concept shall also
carry through directly to each piece of equipment.
2.2.4 Battery Return Configuration DC-I
Equipment battery return configuration shall be DC-I. Equipment configured with the battery
return and chassis ground bonded together (DC-C) shall not be deployed in the network. The
DC-C configuration cannot be utilized with dual plant operation.